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MAGNETISM Magnetism is a force that acts at a distance and makes a magnet: Magnetism is a force that acts at a distance and makes a magnet: Attract and repel other magnets Attract and repel other magnets Attract iron, nickel, cobalt and a few other substances. Attract iron, nickel, cobalt and a few other substances.

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Simple activity to identify the poles of a magnetic dipole A dipole is a pair of electrical charges or magnetic poles of equal magnitude but opposite polarity, separated by some (usually small) distance. The direction of the dipole moment corresponds to the direction from the negative to the positive charge or from the south to the north pole. Permanent magnets mean that the material maintains a magnetic field with no external help. The characteristic of any magnetic material to do so is called retentivity.

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Simple activity to identify the poles of a magnetic dipole ACTIVITY ACTIVITY SUSPENDING A MAGNET SUSPENDING A MAGNET 1. Have a magnet freely suspended so that it can swing in a horizontal plane. 2. Wait until it comes to a rest in an approximate north- south direction after oscillating to and fro for a short time. 3. The magnet may be regarded as having a magnetic axis and it would come to rest with this axis in a vertical plane called the magnetic meridian. 4. The pole which points towards the north is called the north seeking or simply N pole; the other is called the south seeking or S pole.

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MAGNETISM MAGNETIC FORCES

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Simple experiment which show that a repulsive force exists between like poles and attractive force between unlike poles EXPERIMENT: Action of One Magnet on Another. EXPERIMENT: Action of One Magnet on Another. 1. Suspend a fairly strong magnet. 2. Put the N pole of the magnet near the N pole of another magnet; repulsion would occur. (Repulsion would also occur with two S poles). 3. Put the N pole of the magnet near the S pole of another magnet; attraction would occur. It can be concluded that like poles repel and unlike poles attract.

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Simple experiment which show that a repulsive force exists between like poles and attractive force between unlike poles Unlike magnetic poles attract. Like magnetic poles repel. Like magnetic poles repel.

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Effects of the separation of magnets on the magnitude of the force between them When a strong magnet is placed on a balance (north pole facing up) and the reading is recorded, a second magnet is placed directly above the magnet (north pole facing down). When a strong magnet is placed on a balance (north pole facing up) and the reading is recorded, a second magnet is placed directly above the magnet (north pole facing down). The balance reading would increase due to the repulsive forces between the magnets. The balance reading would increase due to the repulsive forces between the magnets. If the distance between the magnets gets closer, the repulsive force would increase. If the distance between the magnets gets closer, the repulsive force would increase.

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Effects of the separation of magnets on the magnitude of the force between them The force of attraction between magnets depends: The force of attraction between magnets depends: 1. Directly on the strengths of the magnets 2. Inversely on the square of their distance apart. The closer the two magnets are the greater the force between them.

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Differentiate between magnetic and non magnetic materials Magnetic Materials Materials such as iron, cobalt and nickel. Attracted to magnets. The domains of the magnetic fields align themselves in an orderly fashion. Consists of tiny magnets called domains which has its own north and south pole. Has strong magnetic alloys that are described as ferromagnetic. Non Magnetic Materials Materials such as copper, glass, brass and wood. Not attracted to magnets. The domains of the magnetic fields are randomly aligned and tends to cancel out.

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How a magnet can attract an unmagnetized object A magnet can attract an unmagnetized object by the process of magnetic induction. This is where an unmagnetized material for example steel is place near to or in contact with a pole of a magnet. When it is removed the object would be magnetized. This is because the magnetic field of the magnet is causes the internal molecular magnets or domains of the steel to align themselves in the same direction.